#include"string.h"
#include <intrin.h>

namespace dt
{
    string::iterator string::begin()
	{
		return _str;
	}

    string::iterator string::end()
	{
		return _str + _size;
	}

    string::string (const char* str)  //构造函数
        :_size (strlen(str))
    {
        _str = new char[_size + 1];
        _capacity = _size;
        strcpy(_str, str);
    }

    string::string (const string& s)  //拷贝构造
    {
        _str = new char[s._capacity + 1];
        strcpy (_str, s._str);
        _size = s._size;
        _capacity = s._capacity;
    }

    string::~string()                  //析构函数
    {
        delete[]_str;
        _str = nullptr;
        _size = _capacity = 0;
    }

    const char* string::c_str() const
    {
        return _str;
    }

    size_t string::size() const
    {
        return _size;
    }

    char& string::operator[](size_t pos)
    {
        assert (pos < _size);
        return _str[pos];
    }

    string& string::operator=(const string& s)
    {
        if (this != &s)
        {
            char* tmp = new char[s._capacity + 1];
            strcpy (tmp, s._str);
            delete[] _str;
            _str = tmp;
            _size = s._size;
            _capacity = s._capacity;
        }

        return *this;
    }

    void string::insert (size_t pos, char ch)        //插入单个字符
    {
        assert (pos <= _size);
        
        if (_size == _capacity)
        {
            size_t newcapacity = _capacity == 0 ? 4 : _capacity * 2;
            reserve (newcapacity);
        }

        size_t end = _size + 1;
        while (end > pos)
        {
            _str[end] = _str[end - 1];
            end--;
        }

        _str[pos] = ch;
        _size++;
    }

    void string::insert (size_t pos, const char* str)   //插入字符串
    {
        assert (pos <= _size);
        
        size_t len = strlen(str);
        if (_size + len > _capacity)
        {
            reserve (_size + len);
        }

        size_t end = _size + len;
        while (end > pos + len - 1)
        {
            _str[end] = _str[end - len];
            end--;
        }

        memcpy(_str + pos, str, len);
        _size += len;
    }

    void string::push_back(char ch)
    {
        insert(_size, ch);
    }
 
    void string::append(const char* str)
    {
        insert(_size, str);
    }

    string& string::operator+=(char ch)
	{
		push_back(ch);

		return *this;
	}

    void string::erase (size_t pos, size_t len)
    {
        assert (pos < _size);

        if (len >= _size - pos)
        {
            _str[pos] = '\0';
            _size = pos;
        }
        else{
            strcpy(_str + pos, _str + pos + len);
            _size -= len;
        }
    }

    size_t string::find(char ch, size_t pos)
	{
		for (size_t i = pos; i < _size; i++)
		{
			if (_str[i] == ch)
			{
				return i;
			}
		}

		return npos;
	}

	

    void string::swap(string& s)
	{
		std::swap(_str, s._str);
		std::swap(_size, s._size);
		std::swap(_capacity, s._capacity);
	}

	string string::substr(size_t pos, size_t len)
	{
		// len大于后面剩余字符，有多少取多少
		if (len > _size - pos)
		{
			string sub(_str + pos);
			return sub;
		}
		else
		{
			string sub;
			sub.reserve(len);
			for (size_t i = 0; i < len; i++)
			{
				sub += _str[pos + i];
			}

			return sub;
		}
	}

	bool string::operator<(const string& s) const
	{
		return strcmp(_str, s._str) < 0;
	}

	bool string::operator>(const string& s) const
	{
		return !(*this <= s);
	}

	bool string::operator<=(const string& s) const
	{
		return *this < s || *this == s;
	}

	bool string::operator>=(const string& s) const
	{
		return !(*this < s);
	}

	bool string::operator==(const string& s) const
	{
		return strcmp(_str, s._str) == 0;
	}

	bool string::operator!=(const string& s) const
	{
		return !(*this == s);
	}

	void string::clear()
	{
		_str[0] = '\0';
		_size = 0;
	}

	istream& operator>> (istream& is, string& str)
	{
		str.clear();
		char ch = is.get();
		while (ch != ' ' && ch != '\n')
		{
			str += ch;
			ch = is.get();
		}

		return is;
	}

	ostream& operator<< (ostream& os, const string& str)
	{
		for (size_t i = 0; i < str.size(); i++)
		{
			os << str[i];
		}

		return os;
	}
}
